What could prevent a 64-bit guest from booting on a new host?

The inability for a 64-bit guest to boot on a new host can often stem from whether virtualization support is enabled in the system's BIOS settings. Specifically, features like AMD-V (for AMD processors) and Intel VT (for Intel processors) are essential for running 64-bit guests because they allow for hardware-assisted virtualization. When these options are not enabled, the hypervisor cannot access the necessary virtualization resources, and as a result, the 64-bit guest operating system will fail to boot.

Enabling these options in the BIOS is critical for compatibility with and support for 64-bit virtual machines. Without them, the host cannot properly manage the guest's CPU virtualization needs, leading to issues during the boot process. This situation highlights the importance of ensuring that virtualization settings are correctly configured in the BIOS before attempting to run 64-bit operating systems in a virtualized environment.